A panel of this type is known, for example, from EP 1 650 375 A1. This type of locking implemented with this panel is preferably provided on the transverse side of floor panels. But it can also be provided on the longitudinal side or on both the longitudinal and the transverse sides. The tongue element is made of plastic and is inserted into a groove extending horizontally on one of the lateral edges and is beveled on its top side. Like a door latch, the bevel causes the tongue element to be pressed inward into the groove by the panel to be newly fitted when the bottom side of this panel touches the beveling and is lowered further. When the panel to be newly attached has been lowered completely to the tuider-floor, the tongue element snaps into a groove introduced horizontally in the opposite lateral edge and locks the two panels in the vertical direction. Special injection molding tools are required for the manufacture of this tongue element, so that the production is relatively expensive. Furthermore, a high-quality plastic has to be used to provide adequate strength values, which makes the tongue element even more expensive. If plastics with insufficient strength values are used, this leads to relatively large dimensions of the tongue elements, since this is the only way to ensure that corresponding forces can be produced or transferred.
The fact that the locking element is embodied as a separate component causes additional expenses. For technological reasons the production of the locking element takes place in a location separate from the panels, so that an integration into the continuous production process, in particular for floor panels, if anything is impossible. Because of the different materials, wood material on the one hand and plastic on the other hand, it is complex and cost-intensive to match the manufacturing tolerances from two separate production processes. Since the locking in the vertical direction would be ineffective if the locking element were missing, this element must further be safeguarded from falling out of the groove introduced into the lateral edge during the further production process and during transport. This securing is also complex. As an alternative, the locking element could also be provided separately to the consumer.
With increasing frequency the floor panels under discussion are laid by do-it-yourselfers, so that it is basically possible through a lack of experience for the required number of locking elements to be misjudged at first and for them not to be procured in an amount sufficient to finish a room. Furthermore, it cannot be ruled out that the do-it-yourselfer may make a mistake when inserting the tongue element, which means that the locking is not possible in an exact manner and causes the interconnection to release over time, which the consumer then incorrectly attributes to the quality delivered by the producer.
From DE 102 24 540 A1 panels are known that are profiled on opposite lateral edges such that hook-shaped connecting elements form for locking in the horizontal direction. For locking in the vertical direction, the connecting elements are provided with form-fitting elements spaced apart from one another horizontally and vertically and with undercuts corresponding to them with one horizontally oriented locking surface each. The transverse extension of horizontally oriented locking surfaces of this type is about 0.05 to 1.0 mm. The dimensioning must be so small for the joining of two panels to remain possible at all. But this inevitably leads to the fact that only small, vertically directed forces can be absorbed, so that extremely low tolerances must be used during manufacture to ensure that the connection does not spring open with normal stress even in the case of minor floor unevenness and/or soft undersurfaces.